The present invention concerns the off-line measurement of components in gas samples taken from the human body, for example exhaled air and in particular samples containing nitric oxide and a system for the collection, storage and/or transport of said samples.
That exhaled air contains a complex mixture of gases was observed long ago but the understanding of the clinical importance of these gases is still increasing. For example nitric oxide has been identified as a marker of inflammation in the airways. Further, certain volatile organic compounds have been linked to metabolic disorders, ammonia has been linked to gastric disorders and carbon dioxide is a well known marker of the gas-exchange function of the lungs.
It has inter alia been shown that the level of nitric oxide (NO) in exhaled air of a human subject is indicative of certain disorders (diseases) including risks for acquiring them. This concept has been shown useful at least for the diagnosis of inflammatory conditions of the airways, such as allergic asthma and rhinitis, and respiratory tract infections in humans, and Kartagener""s syndrome. In particular infections in the lower respiratory tract may be diagnosed. Systems for the determination of NO levels in exhaled air and diagnostic methods for disorders related to abnormal NO levels have been disclosed in earlier patent applications by the present inventors, for example WO 95/02181 (Kjell Alving et al.) and WO 93/05709 (Lars E. Gustafsson).
The principle of analysing human gas samples, such as samples of exhaled air or gases taken from body cavities, such as from the lumen of the intestines offers many advantages, such as ease and speed. The collection of the samples is non-invasive, painless and thus suitable for both infants and sensitive or weakened patients. Hitherto, the known methods have almost exclusively involved on-line measurements, i.e. the air sample has been directly led or aspired to the inlet of a gas analyzer. When the gaseous component to be determined is nitric oxide, a suitable analyzer is for example a chemiluminescence system (e.g. the Sievers Model 280 Nitric Oxide Analyzer NOA(trademark)).
In some cases, exhaled air has been sampled in an intermediate container, such as a syringe, and within a short period of time, injected into the analyser. It has also been attempted to collect air samples in simple balloon-like containers, such as metal coated Mylar(copyright) balloons. However, the stability of the sample remains poor, as components of the gas sample, such as a sample of exhaled air undergo various chemical reactions during storage.
In a specific application, that is the measurement of volatile organic material in breath samples and in particular ethanol in alveolar breath, different solutions have been suggested:
U.S. Pat. No. 3,618,394 discloses a method and device for storage and preservation of organic gases having a volatile organic constituent capable of being degraded by the action of micro-organisms. According to one embodiment, a container consisting of a length of indium tubing pinched off at both ends is used. According to another embodiment, a container is coated on the inside walls with an anti-microbial agent.
WO 92/05738 discloses a mouthpiece for an apparatus for detecting the presence of alcohol or drugs in the breath of a user, said mouthpiece including a heating collar to prevent condensation and means to trap the majority of saliva and other contaminants.
The introduction of a system and device for collection, storage and/or transport of human gas samples containing inorganic substances, such as exhaled air samples containing nitric oxide would offer numerous benefits. In hospitals, a central laboratory could perform each analysis, thus eliminating the need of investing in several analysers and also guaranteeing that the analysis is performed each time in a standardised manner. Minor clinics and out-patients could mail samples to a central laboratory. This way, the development of certain diseases indicated by an abnormal or altered level of nitric oxide could be followed or the correct medical dose adjusted without repeated visits to the treating physician.
The problems remaining to be solved comprise the question of how to achieve accurate and repeatable sampling, how to ensure easy and safe handling, and maybe most importantly, the issue of sample stability.
The present invention eliminates the problems associated with known practices and devices and, additionally, makes possible the economical and efficient off-line measurement of gaseous components-in gas samples, for example exhaled air of mammals, in particular humans. This is achieved by a device comprising at least one inlet/outlet, at least one sample collection compartment and a reagent compartment according to claim 1 and subsequent claims. Further, the inventors disclose an adapter for use with the sample collection device and a system for their use, as specified in the attached claims.